For me, it depends. My favorite ride is actually a tie between the Pirates of the Caribbean and the Haunted Mansion. Those two attractions are dark rides and they are examples of what I believe WED/WDI did best. Engaging, immersive masterpieces that deal with dark subjects with a certain humor that balances out the more terrifying aspects of the content itself (i.e. themes of life and death). I personally believe the placement (at least with Disneyland itself) in New Orleans Square is fitting because those were two dark rides that handled those subjects in a similar manner (or manor, pun intended).
I also partial, though, to Mr. Toad's Wild Ride and Peter Pan's Flight as well as It's a Small World and Space Mountain. I love dark rides in general and it's not even exclusive to Disneyland or any other Disney park. For example, one of the greatest Imagineers of all time, Rolly Crump, designed a dark ride for Knott's Berry Farm in the mid-1970's and Knott's Berry Farm is bringing a new version of it for the 21st century. However, the point is that I LOVE dark rides so much, especially if they're built in the 1950's-80's.